Volume 23, Number 1
1999

Archival Storage Rooms

The other day I was reading the new Tappi Journal,
and a business card in the "Supplier Update" section caught my eye.
It said "Modular Paper Testing Rooms -Custom-built, Turnkey
installations - Guaranteed to meet the TAPPI test atmosphere
standard."

Thinking that these modular rooms might be useful in libraries
and other collection-holding institutions, I called the company,
Environmental Growth Chambers, and spoke with Charlie Briggs (tel:
800/ 321-6854; fax 440-247-87 10). It turns out that these rooms are
already being used to provide controlled environments for
collections. I talked Mr. Briggs into telling us something about
them and describing how they are used in the various institutions
that have them. His response follows.

E. McCrady, ed.

Since 1952, Environmental Growth Chambers (EGC) has
supplied controlled research environments for agricultural,
industrial, and government agencies worldwide, from phone-booth size
cabinets to rooms 5000 feet square, with precisely controlled
setpoints for temperature from below -40°C to over 80°C, and
relative humidity from below 2% to over 95%. For me, some of
the most interesting are paper testing laboratories ("TAPPI rooms")
for companies like Champion Paper and Union Camp; special storage
rooms for documents at the Library of Congress and National
Archives; and the Evidence Rooms at the new Secret Service
Headquarters.

Some characteristics of rooms designed for these purposes are
described below.

Insulation . The location and construction of the room
should make it possible to maintain a constant wall, floor, and
surface temperature close to the desired operating temperature. All
surfaces, including ceiling and floor, should be well insulated,
finished and sealed.

Special HVAC equipment . Far more than just an adaptation
of comfort air conditioning equipment is required. Even units
designed to protect electronic data processing equipment are usually
inadequate. (Limitations of this kind of equipment include the
humidity sensor's lack of sensitivity and inadequate
humidification.)

Control of environmental conditions. If the room is too
large, temperature control and air distribution could be erratic. If
the room is too small, conditions can be adversely affected by human
activity, especially when the door is opened. An airlock or
vestibule may be required.

We include a mechanical desiccant dryer in the air conditioning
system, continuously removing moisture from the air. Then, to bring
the moisture up to the desired level, steam from deionized or
reverse osmosis water is injected automatically to bring the RH up
to the set point.

Temperature and humidity sensors are located inside the room, and
are aspirated ; that is, room air is constantly blown over
sensors hanging from the ceiling to ensure that representative
readings are being made.

Temperature and RH. TAPPI specifies a temperature of
73.4°F ±2° and 50% ±5% RH for paper
test room design. Lower values are often used for archival storage.
We are

presently doing a 1600 ft2 facility for Brigham Young
University Library at 35°-40°F and 30-40% RH.

Refrigeration. The refrigeration system must be able to
maintain specified conditions under ambient heat loads, including
external air temperature, relative humidity effect, room lighting,
and human traffic. EGC uses a microprocessor-controlled direct
expansion system, with temperature control through the continuous
mixing of liquid and hot-gas phases of refrigerant. Such a design
eliminates on-off cycling, and improves both reliability and the
controller's response time.

Air changes and circulation. To insure uniformity and
close control of conditions, the conditioning equipment will provide
15 to 30 air changes per hour. Large ductwork insures lower
velocities, with numerous inlets in the ceiling and air returns
located around the periphery, closer to the floor.